The use of axle/suspension combinations in the light, medium, and heavy-duty truck industry is long established. In these industries, it is well known and conventional to employ a suspension between the frame of a vehicle body and an axle of a vehicle in order to absorb road forces/vibrations which would otherwise normally translate to the vehicle body and/or interior or load through the wheels. Furthermore, the use of auxiliary lift axles (e.g. axles which may be selectively engaged and disengaged from the road surface) to increase road safety as well as to bring a vehicle carrying a load into conformance with highway safety laws is well known.
In this respect, an exemplar lift axle/suspension assembly, of a type commonly employed in a heavy duty truck, is popularly constructed of a parallelogram structure in combination with an air bellows located attached to paddles extending from the parallelogram. Generally speaking, the parallelogram structure is comprised of a pair of substantially parallel beam members, which, as assembled, are pivotally mounted to a hanger bracket of a vehicle frame at one end, and, at their other end, are mounted to an axle seat which is affixed via mechanical means to the top surface of an axle (one paddle extending from each beam member). In this manner, the air bellows can be operated (inflated or deflated) to alternately lower and lift the axle into or out of engagement with the road surface by causing the parallel beam members to pivot about the hanger bracket. Typically, a second airspring (air bellows) is provided located between the axle seat and the vehicle frame and is the primary mechanism by which road vibrations are absorbed in addition to supporting a portion of the vehicle load therewith. An example of such a prior axle/suspension assembly is illustrated and described in U.S. Pat. No. 5,403,031 which is commonly owned herewith. An example of a known axle seat is also described therein, and, as may be seen, generally includes a pair of u-bolts for connecting a suspension beam to the axle.
Although conventional axle seats are effective for their purpose, their bulk combined with the manner in which they connect an axle to a suspension beam via difficult assembly with u-bolts presents several drawbacks. More particularly, employing independent axle seats adds weight to the overall axle suspension system (thus reducing load carrying capability), complicates the assembly process, and takes up a greater space envelope under the vehicle frame (primarily because the suspension beams are designed to “sit” on the top of the axle seats located on top of the axle housing). Because excess parts and the weight which accompanies them are undesirable and because undercarriage space under the vehicle is valuable (e.g. additional auxiliary axles may be desired to be employed so that heavier, more profitable loads can be carried), further improvements in the axle/suspension arts are desired.
In addition to the above described drawbacks, the majority of axles found on vehicles today are of a single piece (fabricated or forged) construction and, as such, are heavy and thus difficult to install, service, and manufacture. Still furthermore, if a portion (e.g. axle end, kingpin, or spindle) of a conventional, one-piece axle needs to be repaired or fails, the entire axle must be removed for repair purposes or replaced in the instance of catastrophic damage/failure.
In view of these problems inherent in single piece axle designs, and in view of the various drawbacks regarding conventional axle suspension combinations delineated above, it is apparent that there exists a need in the art for axles and/or axle suspension combinations which overcome the above drawbacks. It is a purpose of this invention to fulfill these needs in the art, as well as other needs which will become apparent to the skilled artisan once given the above disclosure.